1. Field of the Invention
This invention relates generally to a power supply system for a portable computer. More particularly, this invention relates to a new design approach for a power supply system of a portable electronic device. The portable device may be a portable computer. The purpose is to improve the cooling of the electronic circuits and to enhance the heat dissipation in order to further miniaturize the power supply system thus improving the portability by reducing the weight, size and packaging dimensions thereof.
2. Description of the Prior Art
The portability of a notebook computer or a portable electronic device is often adversely affected by the requirement that such devices are commonly accompanied by a portable power supply system to function as an AC-to-DC adaptor for connecting to an AC power source. The weight and size of this companion power supply system adds to the burden and inconvenience in operating the portable devices. Further miniaturization of the power supply system is limited by the design considerations that certain space for heat conduction is required to prevent overheating and damage to the electronic circuits contained in a portable power supply box.
One solution to this limitation is to build the power supply system in the portable devices to include the function for converting an AC input current to a DC output current for operating the devices. However, this built-in configuration imposes additional weight and size to the portable device with the AC-to-DC converter incorporated as permanent built-in parts. The flexibility of a user not to carry such a power supply system is deprived when an AC power source is either not available or not required for a user to use the notebook computer or a electronic device in a portable mode.
A conventional portable power supply system, which includes an AC-to-DC converter for accompanying a notebook computer or a portable electronic device, is shown in FIG. 1. Such a system is most commonly provided electronic circuits supported on a printed circuit board and contained in a plastic case. The plastic case has to be manufactured with insulation materials provided certain structural integrity to with mechanical strength to sustain various physical impacts to the plastic case. Because the plastic case is employed to contain and protect the electronic circuits. The power supply system including the AC-to-DC conversion circuits must be provided to operate with long term reliability under various conditions that various environmental hazards can be imposed on the system resulted from daily use. More importantly, the case has to provide a seal space for containing the electronic circuits such that moistures or particles from the air are prevented from entering into the sealed space containing the power supply circuits. As good insulation and protection are provided by the plastic containing case, the configuration of this conventional power supply system, however, created a sealed space surrounding the power supply electronic circuits where the dissipation rate of heat generated the circuits are significantly reduced.
FIG. 1 shows a prior art portable power supply system 10 which includes a fully enclosed case 15 for containing and protecting a plurality of electronic circuits 20 generally supported on a printed circuit board (PCB) 25. The fully enclosed case 15 prevents foreign contaminants and moistures from entering into the sealed space thus protecting the electronic circuits 20. However, as the fully enclosed plastic case 15 block the air flow between the sealed space and the external environment, the process for heat dissipation by convection is no longer available. The heat generated from the electronic circuits 20 inside the sealed space can only be conducted through the surface of the plastic case 15. As the plastic case 15 is not an effective heat conductive material, in order to maintain certain heat conduction through the plastic case, the size of the plastic case must be kept at certain size to assure sufficient heat dissipation is maintained. The size limitation due to the constraints imposed by heat conduction thus hinders the power supply system 10 from size reduction and the goal of further miniaturization can not be achieved due to this bottleneck.
Therefore, a need still exists for a new system configuration and design method in the art of portable power-supply packaging and manufacture in order to resolve these difficulties and limitations. More particularly, this new system configuration and design approach must be able to provide more effective heat dissipation paths to allow effective conduction or convection of the heat generated by the electronic circuits in the power supply system. By providing this new system configuration with more effective heat dissipation would then enable those of ordinary skill in the art to further reduce the size and weight of the portable power supply systems such that the difficulties and limitations encountered in the prior art may be resolved.